Automatic pressure-reducing valve.



N0..8o6,1o8. PATENTBD DEG. 5, 1905.

y F. L. GLARK.-l t

AUTOMATIC PRESSURE REDUGING VALVE.

APPLIOATIAQN FILED JAN. 15. 1908.

Att'y.

UNITED sTATEs PATENT oEEicE.

FRANCIS L. CLARK, OF PITTSBURG, PENNSYLVANIA, lASSIGrNOR TO THEWESTINGHOUSE AIR BRAKE COMPANY, OF PITTSBURG, PENNSYLVA- NIA,CORPORATION OF PENNSYLVANIA.

AUTOMATIC PRESSURE-REDUCING VALVE.

Specicaton of Letters Patent.

Application filed January 15, 1903- Serial No. 139,159.

l To @ZZ whom it may concern:

Be it known that I, FRANCIS L. CLARE, a citi- .j zen of the UnitedStates, residing in Pittsburg,

In the high-speed-brake equipment as heretofore used a pressure reducingvalve or blow-down valve yhas been applied to the brake-cylinder for thepurpose of limiting the accumulation of a pressure therein to a certainamount in service applications of the brakes and for gradually reducingthe pressure obtained in an emergency application to a predeterminedpoint. Valves of this type are exemplified in prior patent, No. 506,185,of October 3, 1893.

One of the objects of the present invention is to provide a valve ofthis type which will' open and close at substantially the same pressure.4

In the accompanying drawings, Figure is a central sectional view oi avalve embodying my invention; Fig. 2, a side view, and Fig. 3 a plan, ofa portion of the cylinder-bushing,

'showing the V-shaped groove therein; Fig.'4,`

a sectional view'showing a modification, and

Fig. 5 a face view of the slide-valve, showin the triangular port.

.As shown in Fig.- 1 of the drawings, my improved valve device comprisesa casing 1, which may be formed in two' or more parts and having ashoulder or inwardly-projecting offset 3 dividing the interior chamberinto two cylindrical spaces 2 and 14 of different diameters. In thechamber is located a movable abutment having heads 4 and 5,thevalve-head 4 beingof slightly less diameter than the cyf lindricalchamber 14 and adapted to seat against the shoulder 3, at which point atight joint may be made by means of a gasket 15. The piston-head 5 isfitted within a bushing 6,

secured in the chamber 14, the inner diameterl of the bushing beingsubstantially the same as that of the cylinder 2.

In the cylinder Wall or bushing 6 is formed l aV-shaped groove 7, whichis tapered toward its lower end and comprises an escape-portV aroundVthe piston-head 5, the port being open widest when the piston is at itsuppermost or normal position and nearly closed when the piston" isforced down to its ,lowest position.

The movable abutment is provided on its upper side with asuitably-guided stem 12 and on its lower side with a stem 16, engagingthe perforated cap y8, against which the spring 9 bears. Anadjusting-nut 1() is threaded onto thev casing for adjusting vthetension of the spring and is covered by the cap lock-nut 11.

Patented Dec. 5, 1965.

A pipe 13 leading from the brake-cylinder y establishes communicationwith the chamber 2 abovethe sliding abutment. is adjusted to hold acertain pressure-say sixty pounds per square inch-in the brakecylinder,and so long as the brake-cylinder pressure does not exceed this amountthe valve-head 4 remains seated against the oiiset or shoulder 3,preventing the escape of any air from the brake-cylinder. When thebrakecylinder pressure rises above this point, the

`abutment is forced Vdown against the spring and the valve-head 4 moves:away from its seat against the shoulder 3, thus allowing the compressedair at brake-cylinder pressure to pass around the head 4 and act uponthe balancing piston-head 5. This piston-head 5 being substantially ofthe samediameter as the cylinder 2, the eifective abutment area exposedto the brake-cylinder pressure is practically the same after thepistonmoves down as when the valve-head is closed against its seat. If theexcessive brake-cylinder pressure is due to a service application of thebrakes, the piston moves down but a short distance, leaving theescape-port 7 nearly wideA open, and the maximumarea of this port beingcalculated to release'airiromthe cylinder at about the same rate that itmay enter through the graduatingport of the triple valve thebrake-cylinder pressure in service applications is thus limited to apredetermined maximum.

The spring 9 IOO In the case of an emergency application of the brakesunder a'high-pressure system a much greater pressure isfrapidly chargedinto the brake-cylinder, forcing the piston-valve to the lowermost limitof its movement, at .which point the opening of the escape-port is verysmall, thus permitting at iirst a very slow escape of air from thebrake-cylinder, which rate of ow gradually increases as the piston movesupward until the maximum servicepressure is reached, when the valvecloses by the head 4 seating against the shoulder 3.

According to the modification shown in Fig. 4, the upper stem 12 of thepiston extends through a valve-chamber 21, having bushing 17, andoperatesthe slide-valve 18, which engages a seat in the bushing. Thevalve-seat in the bushing is provided with an escape-port 2O and theslide-valve with a triangular-shaped port 19, the widest end of which islocated adjacent to the escape-port 20, as shown when seated against thegasket in normal position. The operation of this form of my improvementis substantially the same as that previously described, with theexception that the escape-port is controlled by the slide-valve insteadoi' directly by the piston. When upon a service application of thebrakes an excessive pressure is produced in the brake-cylinder, thispressure acting in chamber 2 upon the head 4 causes the piston to movedownward to a position where the widest part ofV the port 19 registerswith escape-port 20, which is of equal width. When the piston is movedaway from its seat, the air under pressure passes around the head 4 andacts upon the head 5, so that the effective area of the abutment orpiston exposed to uid-pressure is the same as when said piston isseated. Then as soon as the excess pressure has escaped to theatmosphere the piston returns to its seat and the escape-port 2O isclosed. In case of an emergency application of the brakes the piston isforced suddenly downward to its lowest position, in which only thenarrowest portion of port 19 registers with the escapeport 20, thuspermitting a very slow release of air from the brake-cylinder. This rateof discharge then gradually increases as the slide-valve is moved upwardby the piston until the pressure is suiiciently reduced to allow thevalve to close and the piston is again pressed against its seat orgasket. By means of this construction it will be seen that the pressureat which the valve closes will be substantially the same as thatrequired to open the valve, and this is of great advantage, since inthese valve devices as heretofore constructed the additional areaexposed to pressure when the valve opens causes the same to remain openuntil the pressure has been reduced to a point considerably below thatrequired to open the valve.

It will be evident that various forms of my .improved valve device maybe devised in which an abutment head or Valve which is normally heldagainst its seat is provided with means for balancing the additionalarea exposed to iiuid-pressure when the abutment 0r valve head is movedaway from its seat. It will also be apparent that any desired size ofbalancing-piston may be used for securing a certain predetermined ratiobetween the respective opening and closing pressures.

Having now described my invention, what I claim as new, and desire tosecure by Letters Patent, is-

l. A pressure-reducing-valve device, comprising a casing containing achamber having a shoulder or seat, a movable abutment having a headnormally engaging said seat and means for balancing the additional areaexposed to fluid-pressure when the abutmenthead is moved away from itsseat.

2. A pressure-red ucing-valve device, comprising a casing containing achamber having a shoulder or seat, a movable abutment exposed on oneside to fluid-pressure, a load device for normally holding the abutmentagainst said seat and a balancing-piston which is exposed to theHuid-pressure when the abutment is forced away from its seat.

3. A pressure-reducing-valve device comprising a casing containing aHuid-pressure chamber having a Seat, a movable abutment, and means fornormally holding the same against said seat, said abutment adapted tomove away from its seat under high pressure and having its effectivearea exposed to liuidpressure substantially constant for all positions.

4. A pressure-reducing-valve device comprising a casinghaving aninterior chamber provided with a shoulder or seat, a sliding abutmenthaving a valve-head adapted to engage said seat and a piston-head ot'substantially the same diameter as the chamber above the valve.

5. A pressure-reducing-valve device comprising a casing containing achamber having an annular seat or shoulder, a sliding abutment normallyengaging said seat and having a substantially constant etl'ective areaexposed to Huid-pressure, and a spring acting on said abutment inopposition to the Huid-pressure.

6. A pressure-reducing valve comprising a casing containing a chamberhaving an annular seat or shoulder, a sliding abutment having one headnormally engaging said seat, and another head of substantially the samearea as the chamber above the shoulder, means for establishingcommunication around the iirstmentioned head when the same is moved awayfrom its seat, a spring bearing against said abutment and an escape-portcontrolled by the movement of said abutment.

7 A pressure-reducing-valve device comprising a casing containing achamber having an annular seat or shoulder, a sliding abutment in saidchamber having a valve-head normally seated against said shoulder, abalancing piston-head, an escape-groove in the wall TIO lholding` thepiston seated against said shoul-A der and means for maintaining theeffective area subject to fluid-pressure substantially IO constant forall positions of the piston.

In testimony whereof I have lhereunto set my hand.

FRANCIS L. CLARK.

Witnesses:

R. F. EMERY, EDWARD A. WRIGHT.

